The present invention relates, in general, to two rail sliders, and in particular, to a stiffer slider structure supporting a computer storage transducer in a rotary actuated disk drive.
Today, technology is driving the miniaturization of every component. For a computer mass storage device incorporating a rotating storage medium, both the media and the slider are rapidly shrinking. A few years ago, 5.25 in. disks with 100% sliders were common. Today 3.5 in. disks are popular with 1 in. disks on the horizon. Sliders have likewise become smaller. Today 50% sliders (i.e. one half the length and width of the 100% sliders) are becoming common with 35% sliders on the horizon.
As these components become smaller, the tolerances associated with the manufacture of the miniaturized product become harder to maintain with the result that the actual product performance can vary over a wide range. Moreover, the smaller product may create or exacerbate known problems. For example, in designing a slider which "flies over" the media, a suitable flying envelope is needed. This envelope identifies a maximum to minimum fly height taking into account all manufacturing tolerances and performance fluctuations. Flying outside the envelope may result in potentially significant errors such as the transducer not being able to pick up the signals from the media; alternatively, if the flying height is too close, slider crashes may result.
Fluctuations in flying height across the disk are due primarily to the higher relative disk speed at the outer diameter (OD) than at the inner diameter (ID) and the yaw angle as the slider is moved by the rotary drive across the media. With increasing miniaturization, the increase in yaw angles from the ID to the OD are substantial. These increases exacerbate the fly height problems and thus require better design and greater latitude for manufacturing tolerances.
One prior art solution to constant fly height involves transverse pressurization contour (TPC) rails symmetrically disposed across the width of the slider. Two rails are provided and each of the rails are similarly treated, i.e. they have contours on each side of the air bearing surface for reacting to the air pressure created by the moving media. Ideally, a TPC slider flies at a constant height irrespective of the yaw. TPC, however, suffers from the disadvantage that manufacturing variations may cause substantial changes to fly height; much greater than desired or tolerated by the designer.
In addition, as the slider shrinks in size, the use of TPC results in rails which are increasingly closer to each other causing significant stiffness and externally applied roll moment problems. Roll moments can be externally applied or internally generated. Externally applied roll moments may be due to bent suspension flexures, wires misaligned on the slider or a misapplied load point; internally generated roll moments are determined by the geometry of the slider itself.
Finally, with TPC, numerous surfaces must be precisely shaped over the entire slider width resulting in significant yield problems. For example, defining TPC width dimensions through the use of photolithographic techniques along with chemical etching, reactive ion etching or ion milling, increases the number of defects which may occur in the manufacturing process thus lowering the yield of the sliders.